#1 here, coming to you from sunny Nova Scotia. Yuu-Chan and Ms. S just got back from visiting Dr. C, our wonderful vet. Her verdict is that Yuu-Chan has an infection around the joint of his ankle, probably coming initially from a bite during play. He has a fever and the joint is swollen, but he has been put on antibiotics and a new kind of anti-inflammatory, and he should start to get better very quickly. The trick, actually, will be to keep him quiet as he improves. So, he may have to spend some time in the back room, alone or with just Sei-Chan for company.
I don't have any new photos of him to post as I write this, but how about a nice older one?